Avalanche Advisory

ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.

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The Bottom Line

Even though our snowpack is mostly stable in the Turnagain pass region, there are a few outliers that are keeping the danger at MODERATE today as both cornices and glide avalanches continue to act in unpredictable manners. Fast moving, high volume sluffs and the potential for shallow, fresh wind slabs will also add to today’s concerns.

South of Turnagian Pass harbors a different snowpack structure where we found buried surface hoar responsible for a very large avalanche on Saturday in the Groundhog Creek drainage (Johnson Pass area). If travelling in these areas recognize that we’ve got a persistent weak layer problem in addition to those listed below.

Show the Complete North American Avalanche Danger Scale

North American Public Avalanche Danger Scale

Avalanche danger is determined by the likelihood, size and distribution of avalanches.

Danger Level

Travel Advice

Likelihood of Avalanches

Avalanche Size and Distribution

5 Extreme

Avoid all avalanche terrain.

Natural and human- triggered avalanches certain.

Large to very large avalanches in many areas.

4 High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human- triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

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We'd like to extend a HUGE thank you to everyone who has submitted observations to the avalanche center as of late! The more info we get coming in, the better and more accurate our product will be. Remeber, its quick, easy and greatly appreciated to submit an observation (can be done on a smartphone) using the 'Submit Observation' button.

Avalanche Problem 1

Cornice

Almost Certain

Very Likely

Likely

Possible

Unlikely

Chance

Historic

Very Large

Large

Small

Size

It was impressive to stand on top of a ridge yesterday and look around at literally thousands of tracks littering the Turnagain pass area, and to know that is only a fraction of what was skied, hill-climbed and boot-packed last weekend. Observations yesterday are pointing toward generally stable snow in the heart of the core area, with a couple of exceptions.

Cornices are growing larger by the day and we have seen several fail naturally over the last few days. This is very indicative that many of these are reaching their tipping point and can fail naturally or be sped along by a skier or snowmachiners added weight. With any luck these will fail mid-storm or overnight but often times it is a rise in temperature or direct sunlight that weakens the bonds and promotes failure. Simply avoid time spent below cornices and when travelling along a corniced ridge, stay back much farther than you think necessary to maintain that added margin of safety.

Large cornices hang over the SW Face of Magnum. The horizontal track traversing below the cornice is an example of a very poor route decision. The much safer option would have been to travel along the shaded ridge, well back from the edge. photo credit: Josh Varney.

Avalanche Problem 2

Dry Loose

Almost Certain

Very Likely

Likely

Possible

Unlikely

Chance

Historic

Very Large

Large

Small

Size

In sheltered terrain and mid-slope, where winds have not effected the surface, the snow continues to loosen and facet out. Sluffs will be fast and have the potential to reach high volume in the alpine. Don’t get caught off guard by this in steep, alpine terrain. Getting taken out by your sluff can have very serious consequences in some of the complex and challenging terrain that we’ve seen people travelling to over the last several days.

WIND SLABS:

With 6-8” of loose, unconsolidated snow available for transport above ~2500’, shallow wind slabs could be quick to build and prove tender today. Keep an eye out for active pluming off ridges as a sure sign of wind slab formation. Expect any wind slabs forming today to be shallow (6-12”) but tender.

A few wind plumes yesterday were seen transporting the loose, surface snow into shallow wind slabs on Sunburst.

Additional Concern

Glide Avalanches

The more you look around, the more glide cracks you see in Turnagain pass and surrounding areas. Glide cracks continue to release here and there, without any real discernable pattern. Best practice continues to be to limit your time spent exposed to glide cracks. This takes some doing right now, considering the minefield of glide cracks that Turnagain pass currently is.

This glide crack on Cornbiscuit partially released sometime between Saturday afternoon and Sunday afternoon.

Mountain Weather

Yesterday proved to be quite a pleasant day in the backcountry with partly cloudy skies, temps in the low 20’s at ridgetops and winds in the low teens (mph) from the East.

As fond memories of last weekend’s sunshine and exceptional snow fade into this workweek, we’ll usher in another period of unsettled weather beginning today and ramping up a bit tomorrow. We can expect a few more clouds today along with an inch or two of snow above about 800’. Temps are cool this morning but will be warming through the day and may reach the mid-30’s at 1,000’ by this afternoon. Ridgetop winds are expected to be in the 15-30mph range from the East.

Tomorrow another front will begin to impact our area with potentially a bit stronger winds and more precipitation than what we see today.

PRECIPITATION 24-hour data (6am - 6am)

Temp Avg (F)

Snow (in)

Water (in)

Snow Depth (in)

Center Ridge (1880')

26

0

0

92

Summit Lake (1400')

24

0

0

27

Alyeska Mid (1700')

28

0

0

70

RIDGETOP 24-hour data (6am - 6am)

Temp Avg (F)

Wind Dir

Wind Avg (mph)

Wind Gust (mph)

Sunburst (3812')

19

ENE

11

34

Seattle Ridge(2400')

22

n/a

n/a

n/a

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Dec 18, 2018 )

AREA

STATUS

WEATHER AND RIDING CONDITIONS

Glacier District

Johnson Pass:

Open

Please stay on trail to avoid resource damage through Forested areas.

Placer River:

Closed

Closed

Skookum Drainage:

Closed

Closed

Turnagain Pass:

Closed

Closed November 21 due to inadequate snow conditions. #hopeforsnow

Twentymile:

Closed

Closed

Seward District

Carter Lake:

Open

Lost Lake Trail:

Open

Please stay on trail to avoid resource damage through Forested areas.

Primrose Trail:

Open

Please stay on trail to avoid resource damage through Forested areas.

Resurrection Pass Trail:

Closed

Closed for the 2018/19 season. Next season will be open to motorized use.

Snug Harbor:

Open

South Fork Snow River Corridor:

Closed

Closed. Forest Service is monitoring conditions.

Summit Lake:

Open

Subscribe to the Turnagain Area Avalanche Advisory:

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Chance of Avalanches

This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches

This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

Chance of Avalanches

This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches

This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. The are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.
This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.